During many types of surgical procedures, for example, open heart surgery, blood is removed from the patient and passed through an extracorporeal circuit for oxygenation and filtration. As the blood that has been removed from the patient passes through the extracorporeal circuit, it may be temporarily stored in an extracorporeal reservoir. One such reservoir used to temporarily hold blood is a venous reservoir. Venous reservoirs are constructed to allow for easy venting of air from the reservoir and may include a mesh to filter blood as it passes through the reservoir. Venous reservoirs may be rigid (hard shell) or soft shell (bag).
Soft shell venous reservoirs are devices used in extracorporeal circulation during cardiotomy procedures as containers for holding blood coming from the venous cannulation of the patient and from an external cardiotomy reservoir that is dedicated to handle blood from the field suckers. In some instances, during operation, it may be necessary to temporarily divert venous blood into a cardiotomy reservoir for storage, instead of the soft shell reservoir.
Soft shell reservoirs have at least one wall constructed from a soft material, for example a plastic sheet. They are typically comprised from a soft bag constructed as a closed system that can change shape depending on the amount of blood stored in them. One advantage of a soft shell reservoir or “bag” is that it will collapse when emptied, thus preventing accidental delivery of air to the patient. Another advantage is that the contact between air and blood in a soft shell reservoir is very limited, thus reducing blood activation during extracorporeal circulation.
Blood flowing into the bag is carried through an inlet port that is typically located near the bottom of the bag. Blood flowing out of the bag is carried out through an outlet port that may be connected to an outlet tube. The outlet port is typically located near the bottom of the bag.
Between the inlet port and outlet port there may be a filter for filtering the blood and removing any solid and gaseous micro-emboli or air. Air that is removed from the blood can gather at the top of the bag and be vented out. There is typically at least one port near the top of the bag to allow air from the blood to exit the bag.